I am working on a friends heavily modified Evo 9 with AEM plug and play, and apparently there is a very weird wire going into pin #91 (knock sensor). The car is bucking really bad at random times and I'm wondering if this wire could be the problem. I haven't been able to log the car to see if the knock signal is going crazy when the "bucking" happens. The picture of this mysterious wire is pictured below:




Any ideas what this thing is and why the ground is just hanging out there like this?

 

did you ever find out why this is just hanging out there? should it be grounded?

 

Knock sensor detects knock.
It does not prevent knock